Simultaneous multianalyte binding assay (SMBA), in which two or more analytes are measured simultaneously in a single assay, represents the next major advance in binding assay methodology. SMBA is important because it uses less sample, the test throughput is increased, and the overall cost per test is decreased. The first SMBA, in which human insulin and growth hormone in serum were measured using two different radioisotope labels was reported in 1966. Since then, various approaches for SMBA have been demonstrated. Many of these involve the use of multiple labels, such as radioisotopes and fluorophores. Other ways of performing SMBA include a microspot assay, a method based on spatially distinct fluorescent areas quantitated by laser-excited solid-base time-resolved fluorometry, and a nonseparation electrochemical enzyme immunoassay using multiple gold films deposited on the same membrane.
Electrochemistry is one of the most sensitive analytical methods, and has been shown to be an effective technique for detection in immunoassay. The assay is based on labels that are either electroactive or catalyze the production of an electroactive product. Electrochemical immunoassay has many features in common with other types of binding assays and one that is less well shared, but very important, in that it can be miniaturized easily. This is especially important in the development of disposable devices and methodology for ultra-small sample amounts. The potential exists to develop simple electrochemical binding assay kits for applications that require small, portable systems.
A simultaneous dual-analyte immunoassay method based on releasable metal ion labels is known. That approach, however, is not generic due to the fact that a different metal label is needed for each analyte, and the detection limit was higher than with enzyme labels.